This invention relates to the preparation of macrocyclic oligomer compositions, and more particularly to the preparation of macrocyclic polyetherimide oligomers.
U.S. Pat. No. 5,357,029 discloses a class of macrocyclic polyimide oligomer compositions not containing spiro(bis)indane moieties. Said compositions may be converted to linear polyimides. By reason of the low viscosities of the oligomer compositions in comparison to the linear polymers, said compositions are capable of employment in areas from which polyimides have previously been barred.
According to said application, the macrocyclic polyimide oligomers are prepared by the reaction of equimolar amounts of at least one tetracarboxylic acid or its dianhydride and at least one diamine. Said reaction requires pseudo-high dilution conditions; i.e., maintenance of the reagents at high dilution. Since the condensation reaction between the acid and the diamine is slow, the rate of reagent introduction must also be slow and the reaction may take several hours to go to completion.
In recent years, there has been an increase in interest in the preparation of polyetherimides, a subgenus of polyimides, by the reaction of substituted bis-phthalimides with salts of dihydroxyaromatic compounds. Reference is made, for example, to U.S. Pat. No. 5,229,482. This reaction normally takes place in the presence of phase transfer catalysts and at relatively high temperatures. Thus, the phase transfer catalysts employed must be stable at high temperatures. Various classes of substituted guanidinium salts having the required stability are disclosed in said U.S. Pat. No. 5,229,482 and in various other patents, particularly U.S. Pat. Nos. 5,081,298, 5,082,968, 5,116,975 and 5,132,423, the disclosures of all of which are incorporated by reference herein.